Differential Headache

So after investigating a suspicious oil trail, we were told by a mechanic that our rear diff on our 1989 Chevy Suburban 1500 is on its way out. One from a wrecker is expensive, and we had another guy bow out on us. I've got a friend with a diff, but I have no idea what the ratio is on our diff. It is a GT4, and I'm looking at getting some friends to help replace it my own damn self.

If someone would be kind enough to tell me what ratio I'm looking for, as well as anything I should know in advance, it would be greatly appreciated. This thing is one step away from being scrapped, and I want to save it. Thanks!

4W You need to check what ratio it has and replace it with the same ratio.
Best to pull inspection plates and read the gear rato off of the ring gear.
Good Luck
MT

take of the diff. cover count the teeth on the ring gear &the teeth on the pinion. to tell the ratio.determine how many times the pinion has to turn before the ring gear makes one full revolution thats your ratio. on a 3:42 ratio axle the pinion turns almost 3and 1/2 times to the ring gears one revolution. exwldr.......

I think gt4 is 3.73 ratio. So if it has not been messed with before, it should be 3.73..

I have been looking for a gu6 ratio (3.42) for my Z71 pick up off and on.
Good luck, I hear the carriers break easily. Which is probably why I havent stumbled across one for mine yet....